The development of a latent electrostatic image with a liquid electrostatic developer and transfer of the developer to a carrier sheet where the image is fixed by heating is known. For example, Landa et al. U.S. Pat. No. 4,411,976 describes a method of transferring a liquid-developed electrostatic image across a gap to a carrier sheet and raising the temperature up to 100.degree. C. to solvate binder which surrounds a pigment in the developer and thereby spread the transferred image to form areas of the image which are dense. Landa U.S. Pat. No. 4,413,048 describes resinous-toner particles, e.g., polymer encased pigment particles, together with spacer particles incorporated within a nonpolar liquid, e.g., low boiling aliphatic hydrocarbon. These and other patents describe pigments coated with various polymers, resins, and waxes and dispersed in a nonpolar liquid to serve as liquid developers. Japanese Patent Publication No. 60-39229 published Sept. 5, 1985 describes a liquid developer for electrostatic imaging wherein the colorant, e.g., a combination of colored pigment and carbon black is dispersed with a composition of a specifically defined binary or ternary copolymer and a waxy substance of polyolefin having a softening point of 60.degree. to 130.degree. C. The colorant is carbon black or preferably carbon black and an organic pigment in cake form containing water treated by flushing, i.e., replacement of the water present by a resin solvent solution. The water and resin solvent are subsequently removed and the lumps of resin coated pigment material are pulverized to form fine powder of flushed pigment. A resin dispersion is prepared from binary or ternary copolymers obtained from the polymerization of acrylate monomers in aliphatic hydrocarbon liquid in the presence of a waxy substance or polyolefin. The flushed pigment, a resin dispersion as defined, and a nonaqueous solvent are then dispersed in a high shear mixing device to break up agglomerates and form the liquid developer.
It has now been found that an improved liquid electrostatic developer can be prepared using a flushing technique for preparing pigment without need for special resins. The images formed using the liquid electrostatic developer by this process have improved image quality manifested by reduced squash, improved resolution, and improved transfer efficiency.